1. Field of the Invention
This invention relates in general to a cellular communication systems, and more particularly to mobility management for terminals with multiple subscriptions.
2. Description of Related Art
Two technical developments that have had a direct effect on the lives of millions over the past few years are the Internet and the mobile phone. While the Internet has allowed easy and inexpensive access to a wealth of information, independently of its location, the mobile phone on the other hand has broken the tie between location and access to communication.
The logical next step is to bring these two technologies together, allowing access to information that is not only independent of the source of the information, but also independent on the location of the person accessing it. Already, people are beginning to see that they need not restrict their use of mobile phones to when they are on the move. However, the mobile phone is now becoming a necessity in offices and homes alike. A mobile phone offers a single point of contact through one number, anytime, anywhere, and voice communications are not the limit. Rather, data communications capabilities are growing because they are demanded by traveling business executives. These habitual travelers must be able to access data in real time, as and when they need it.
For example, smart messaging is bringing Internet services to every mobile user""s fingertips. As we become used to the freedom mobile communications provide, we will become more demanding about the information and services required to benefit our lives.
For cellular telephony to continue its spectacular growth, it must handle more subscribers per basestation and higher-bandwidth services. Toward that end, the industry""s third technology generation (3G) is envisioned as a move beyond voice-only terminals to information communicators that will pass images and data.
Europe""s Universal Mobile Telecommunications Standard (UMTS) is the follow-on to the second-generation Global System for Mobile communications (GSM) digital cellular standard. The Universal Mobile Telecommunications System (UMTS) is intended to provide a worldwide standard for personal mobile communications with the mass-market appeal and quality of wireline services. Over recent years, digital cellular technologies, such as GSM, have led the way towards personal communications, making mobile communications available to millions of users all around the world at reasonable cost. But to match the UMTS vision, a communications system must include support for flexible bearer and bandwidth-on-demand services for local (indoor) environments and for wide area coverage; a variety of mixed traffic types and relevant charging capability for mobile multimedia applications; customized services, service creation environments and service flexibility using, for example, intelligent network (IN) tools; and wideband wireless local loop (WLL) enhancement to the fixed network.
Nevertheless, today the mobile standards landscape is an often confusing collection of technologies. The first cell-phone generation is represented in North America by the 800-MHz analog Advanced Mobile Phone Service (AMPS) system, along with IS-54 digital AMPS. Europe moved quickly past its first generation (NMT, TAC and ETACS), deploying the 2G time-division-multiplex (TDMA) GSM system at 800 MHz. In North America, 2G is now being deployed at 1.8 GHz in the form of IS-95A CDMA, IS-136 TDMA and what is essentially European GSM at a higher carrier frequency.
Some technologies are dominant in some geographical areas. Here we see the impetus for multi-mode: to combine different standards to provide ubiquity of services.
Thus, for example, a telephone for business people who travel worldwide may have to integrate GSM, DCS-1800 and PCS-1900 functionality, and perhaps also AMPS to widen the area of usability still further. And the melting-pot of new communications technologies is continually generating intriguing possibilities which are fast crystallizing into reality: handsets that combine a standard like DECT (the standard for digital European cordless telephony) for local-loop service with a wide-area technology like GSM or AMPS; DECT base stations that seamlessly integrate voice and data from multiple phone extensions within the home and transmit it as Integrated Services Digital Network (ISDN); networks for dual-mode data terminals which combine islands of high-data-rate service using DECT with wide-area coverage using GSM or another technology.
In current second generation cellular systems (GSM, IS-95/IS-41, IS136/IS-41, etc.), there is only one subscription in a mobile terminal. Each subscription is specified by a set of services and an identity. In GSM, the subscription is physically housed in a Subscriber Identity Module (SIM) card, and the subscription identity is the International Mobile Subscriber Identity (IMSI). A temporary identity (Temporary Mobile Subscriber Identity or TMSI) can also be assigned by the network, to be used in lieu of the IMSI. The existing mobility management procedures are all based on that single subscription assumption. For example, the GSM Location Area Update procedure, which is used to update the network on the terminal""s location, is carried out for a given IMSI or TMSI. Another example is the paging procedure. The paging request specifies which IMSI or TMSI is being paged. The above are examples from GSM, but the single subscription assumption in mobility management is true in all second generation cellular systems.
The above mentioned UMTS has envisioned a mobile terminal with multiple subscriptions. These subscriptions may be referred to as UMTS Subscriber Identity Module (USIMs), wherein each are identified by a unique USIM-ID or identification code. Clearly, current mobility management schemes have to be extended to meet the multiple USIMs requirement. A straightforward extension would be to carry out the procedures (e.g. location area update) separately and independently for each USIM. The major drawback is that information common to USIMs is repeated (e.g. physical location of terminal), thus leading to inefficient signaling and waste of radio resources. There is also a waste of processing load on the terminal and the various network nodes. Finally, the bit space available for TMSI would be depleted faster if each USIM were assigned a different TMSI.
It can be seen that there is a need for mobility management for terminals with multiple subscriptions.
It can also be seen that there is a need for a scheme which integrates the USIM-specific procedures into single procedures, and which uses a common TMSI.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a scheme for providing mobility management for terminals with multiple subscriptions.
The present invention solves the above-described problems by providing a scheme which integrates the USIM-specific procedures into single procedures, and which uses a common TMSI.
A method in accordance with the principles of the present invention includes allocating an UMTS subscriber identity module for each subscription associated with a mobile terminal, each UMTS subscriber identity module being identified by a identification code and performing a location area update by providing a single location area update request message comprising a list of identification codes for each UMTS subscriber identity module associated with the mobile terminal.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the single location area update request message is provided to the network for authentication, wherein the method further comprises separately authenticating by the network each subscription represented by the identification codes.
Another aspect of the present invention is that the single location area update request message comprises USIM_IDSs listed in sequential order.
Another aspect of the present invention is that the terminal and network each build their own Ordered List of Registered USIM-IDs (OLRU) which records the USIMs that succeeded.
Another aspect of the present invention is that the network assigns a Base TMSI.
Another aspect of the present invention is that subsequent Location Area Update procedures use the Base TMSI, which is common to all USIMs in the OLRU and therefore the Base TMSI does not have to be repeated for each USIM.
Another aspect of the present invention is that paging request uses the Base TMSI, along with a USIM Specifier (USIMS) field, which specifies which USIM(s) is being paged.
Another aspect of the present invention is that USIMS is kept very compact with bit string coding, which also gives flexibility to page multiple USIMs at the same time.
Another aspect of the present invention is that the terminal and network interpret the bit string by using the OLRU.
Another aspect of the present invention is that the terminal has to listen to only one paging subchannel which is determined by calculating the sum modulo N of the last digits of the USIM-IDs in the OLRU, and wherein N is the number of possible subchannels.
Another aspect of the present invention is that the scheme applies to UMTS as well as GSM/GPRS, if GSM/GPRS is enhanced to support multiple subscriptions per terminal.
Another aspect of the present invention is that the present invention applies to IS-95/IS-41, IS-136/IS-41 systems, if they evolve to multiple subscriptions per terminal.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.